Reference may be made to the following United States Patents of interest: U.S. Pat. Nos. 4,193,541; 4,132,354; 1,872,213; 1,630,591; 3,860,038; 3,749,108.
It is desirable to provide a damper device which may be readily installed into conduits, such as ducts or flues of existing heat producing units such as in homes, industrial plants, etc., and which may also be readily included with new installations of such heat producing units. Typically, the installation of presently existing damper devices requires a portion of an existing flue to be cut out and removed so that the damper device and a corresponding flue adapter portion may be fitted therein. An example of such a prior device is shown for instance in the aforementioned U.S. Pat. No. 4,193,541. The disadvantage of such units is that they require both cut ends of the flue to be supported while the damper unit is installed.
Therefore, it is particularly desired to provide a damper device which can be installed in existing flues without cutting through the flue and removing a complete portion of the flue, and yet enabling the damper device also to be readily installed in new installations.